1. Field of the Invention
This invention relates to integrated circuit packaging technology, and more particularly, to CDBGA (Cavity-Down Ball Grid Array) packages.
2. Description of Related Art
The BGA (Ball Grid Array) package is an advanced type of integrated circuit packaging technology, which is characterized by the use of a substrate as a chip carrier in which a top surface is used for mounting one or more semiconductor chips and a bottom surface carries an array of solder balls (i.e., a ball grid array). During mounting using SMT (Surface Mount Technology) processes, the BGA package can be mechanically bonded and electrically coupled to an external printed circuit board (PCB) by means of the solder balls.
The CDBGA (Cavity-Down Ball Grid Array) package is a special type of BGA technology in which the packaged semiconductor chip is mounted in an upside-down manner within a downward-facing cavity in the substrate. As the CDBGA package has come into use, semiconductor chips have become smaller and have come to operate at substantially higher speeds generating large amounts of heat. The heat must be dissipated from the semiconductor chip and this requires heat sinks attached to the semiconductor chip.
One problem of the CDBGA, however, is that the process of attaching a heat sink on the active surface of the semiconductor chip often breaks the integrated circuit. Still another problem is that the heat sink comes in contact only with a localized point on the semiconductor chip rather than having an evenly distributed contact over the active surface of the packaged semiconductor chip. As a result of the point contact, the heat-dissipation efficiency is low.
A solution which eliminates these problems has been long sought but has equally as long has eluded those having skill in the art.
A cavity-down ball grid array (CDGBA) package includes a substrate having a through cavity provided therein. A heat sink is attached to the substrate and a semiconductor chip in the cavity is attached to the heat sink and electrically connected to the substrate. A ball grid array is on the substrate and on the semiconductor chip. By having a portion of the ball grid array on the semiconductor chip, increased heat-dissipation efficiency is achieved by dissipating heat from the active surface of the packaged semiconductor chip. This also increases the wire-bonding routability on the packaged semiconductor chip by allowing the bonding wires connected to the packaged semiconductor chip to be spaced at larger intervals to help reduce the capacitive effect and thereby improve the electrical performance of the packaged semiconductor chip.